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View Full Version : C64 tape duplicator - vintage hackery for Zetr0, rkauer, etc



Merlin
19th June 2009, 23:07
One for the reverse engineering specialists here, i.e. Zetr0, rkauer, etc..

This was posted on Lemon 64 by Arkanoid, with questions as to who may have built it.
[attachment=2:3plcn4pr]47518353.jpg[/attachment:3plcn4pr]
[attachment=1:3plcn4pr]70500568.jpg[/attachment:3plcn4pr]
[attachment=0:3plcn4pr]11061562.jpg[/attachment:3plcn4pr]

Apart from a fine piece of 80s hackery, I was wondering about the design of this beastie. From what I can make out, the unit includes a mains neon indicator, two LEDs, a resistor or two, a fuse holder, a few capacitors (hard to tell what rating and if electrolytic or not), a couple of switches, two 5v power supplies (you can see the transformers through the holes in the internal boxes) and a chip, which I believe to be an SN7416N Hex inverter / driver IC.

Now, apart from the obvious crossover of the read/write lines from one datasette to the other, I was wondering about the data LEDs and the SN7416N; it is possible that the person that designed this is using the SN7416N to clean up and buffer the signal between the two cassette drives, along with maybe driving the data LEDs?

The reason I am wondering if you guys could help me work out how this unit works is because I can maybe add some of the features of this into the updated C64S adapter I am designing; the unit I am drawing up will use an external power supply, to save power being drawn from the MIDI / Joystick port (which new PCs won't have as standard) and also to possibly provide a standalone duplication facility like this unit.

If you have any ideas about this, I'd like to hear them.
:thumbsup:
Thanks

Merlin
21st June 2009, 00:12
Righty-Ho,

After much deliberation and study of this device along with a couple of other PC to C64 datasette interfaces, I finally think I am getting somewhere. I am designing the unit to be able to take a cheap external unregulated transformer to provide the power, which I am stabilising with a 78L05 regulator. Using the power socket option also allows for a couple of options for this design as follows.

1. A joystick port to power jack adapter can be used if you need to use the PC to provide the 5v supply.

2. Using an external power supply allows this unit to be used as a standalone datasette duplicator, if I have designed this correctly.

I am using a SN7416N inverter to clean the signal up from the read device and feed a cleaner signal to the write device, with little or no loss in signal quality. I have also allowed for the option to use spare gates on the SN7416N to drive optional 'Data' LEDs, to indicate that data is being transferred and to indicate when file transfer from the 'read' device is complete, as the LED will go out if no data is being transferred (I think!)

This unit is based on the X1541 cable design as well as Markus Brenner's C64S interface. This unit should allow TAP files to be written back to a new tape via a PC and also allow for tape-to-tape duplication for backing up tapes. It should still allow for connecting a 1541 drive to the board, for transferring disk files.

@ TC / Zetr0 etc.

Can somebody please check that I haven't cocked anything up with this design, or maybe missing something out from the schematic?

[attachment=0:3r5z0z66]Upgraded C64S version 1 - draft.gif[/attachment:3r5z0z66]

Thanks

Zetr0
21st June 2009, 02:15
Looks good m8,

I cannot see it blowing up :D

the only thing concerning me is the 7416N directly driving LED's for Read / Write and READ / Write Data, but to be fair, if you got a good solid +5VDC you wont have any problems.

rkauer
21st June 2009, 02:52
Since just two leds are used, use a transistor for each one, TTL ports can't handle that much current (15~25mA) :roll:

OK, no joking: using mini-leds you are OK (12~15mA). Just calculate the current to be 10mA or a bit less.

TheCorfiot
21st June 2009, 12:50
@Merlin

Looks good, I think you need to add some resistors inline with the anode drives for the LED's to limit the current draw..

Breadboard prototype time :thumbsup:

TC :D

Merlin
21st June 2009, 13:02
Thanks guys, I haven't designed anything like this in a LONG time..... :thanks:

I'll add a couple of 10k resistors to the LED + lines and use mini LEDs as Rogerio suggests; I have enough of them knocking around here.

OK, the next step will be a stripboard prototype without the 6 pin DIN, to test the standalone capability and TAP writing ability of the design. If I've got it right, the unit should light the 'write' LED while the PC writes the TAP file to the datasette, to confirm that data is being written.

Just don't expect a neat prototype..... :woot:

Edit: Schematic updated to show alternative power adapter and added 10k resistors to LED + lines.
[attachment=0:168ajg29]Upgraded C64S version 1.1 - draft.gif[/attachment:168ajg29]

Zetr0
21st June 2009, 17:57
@Merlicious

Hiyas m8y,

after reading the posties from rkauer and TC, I hit the spec for the 7416N, it wont provide enough juice really m8,

what you need is a transistor collector connected to the 7416N #3 READ out , put the +5 in on the transistor base then have the a 10k from the emitter of the transistor to the Anode (LED )

heres a schematic to help.. it uses an NPN 2N3019 Transistor... very common and less than pennies.

please check the schematic m8... I have had a fair few beers m8, being BBQ weather here :D *hic* so a double or best tripple check emmiter and base LOL!



good luck m8y

rkauer
21st June 2009, 19:08
@Zetr0: masta flux, you made a mistake! :wooha:

Collector of the transistor must be hooked to +5V, use the base connected to the signal gate via a small resistor (1.5k up to 47k) or the transistor will load the gate.

Zetr0
21st June 2009, 19:11
yep... i knew must of done.... LOL

(Base signal and Collective Power)

thats 6 bottles of Newcastle Brown (aka Bottle of Dog) and 6 576cl cans of Stella (necter of the gods)

Sorry Merly, and great catch RKauer....

okie.... back to the sauce methinks.... I just LOVE BBQ's :D

RedDaemonFox
21st June 2009, 19:15
Maybe you should come back when you're sober travelocity

Zetr0
21st June 2009, 19:30
okay....

attached some relevent pictures

again, please for the love of god, check the schematics, my spell checker is actually smoking from over use right now, and the keys are some what heavy pressing.

but yes... see attached...

Zetr0
21st June 2009, 19:39
Maybe you should come back when you're sober travelocity


you have a thing for Gnomes dont you.... one might even be concered as such.... if i wasn't so er... half cut :D


http://www.funohfun.com/wp-content/uploads/garden-gnome.jpg

Travelocisty indeed!!!

PMSL!!!

Merlin
21st June 2009, 19:59
Take 3......

[attachment=0:2cdgqc38]Upgraded C64S version 1.1 - draft.gif[/attachment:2cdgqc38]

Does this look something like it now?

rkauer
22nd June 2009, 02:13
Looks OK now. :thumbsup:

Zetr0
22nd June 2009, 04:08
Its looking great Merlicious, I cannot wait to see the the proto :D

RedDaemonFox
22nd June 2009, 04:59
just test it on a machine you can afford to fry

Merlin
22nd June 2009, 15:03
Its looking great Merlicious, I cannot wait to see the the proto :D

That is praise indeed, coming from you..... :bowdown:

Thanks

RedDaemonFox
22nd June 2009, 19:05
I see you are on vcforum too, you guys are everywhere

Zetr0
22nd June 2009, 19:11
@Merlicious

I just love a well thought out schematic my friend :D, and cleary shows you have put a lot of thought into it.


I see you are on vcforum too, you guys are everywhere

The internet..... is no longer a safe place.....

RedDaemonFox
22nd June 2009, 21:15
it hasn't been since win95

Merlin
22nd June 2009, 21:38
I see you are on vcforum too, you guys are everywhere

Hey, if it's retro and computing, we are all over it like a cheap suit.....what's wrong with that? EAB and the guys at VCF shared experiences along with Atari-Forums and other retro sites when we worked out Retr0bright, so why should the retro community be compartmented off?

We are like Woody from Toy Story; we see EVERYTHING......... :wooha:

:woot:

Kin Hell
22nd June 2009, 23:06
<snip>

http://www.funohfun.com/wp-content/uploads/garden-gnome.jpg

<snip>

http://rhizome.org/imagebase/article/2286/roflcopter.gif

Kin

Merlin
22nd June 2009, 23:28
:hijacked:

Can we please try and keep this to a technical discussion of my project, please?

:sigh:

Merlin
22nd June 2009, 23:59
Arkanoid has been good enough to temporarily dismantle the unit he has and here is some more 80s retro nekkid amateur hardware pr0n for Zetr0 et al to lust over....

Warning! Totally topless and naked circuit boards below!!

[attachment=2:3luhdl39]40613291.jpg[/attachment:3luhdl39]

[attachment=1:3luhdl39]57366226.jpg[/attachment:3luhdl39]

[attachment=0:3luhdl39]86649743.jpg[/attachment:3luhdl39]

From these, it's conclusive that the large boxes are power supplies. I also think we correctly figured out how the gates on the 7416 were arranged, although I need a 'coffee and paracetamol' moment to dissect the unit fully.

Merlin
23rd June 2009, 21:30
This, after a LOT of coffee, Paracetamol and Photoshoppage, is the circuit diagram for Arkanoid's unit, as far as I can make out:-

[attachment=0:15p5hiyh]Arkanoid.jpg[/attachment:15p5hiyh]

I've asked Arkanoid to check the circuits are mapped correctly and to confirm the colour codes of the resistors as they weren't too clear on his photos.

Kin Hell
24th June 2009, 20:52
:hijacked:

Can we please try and keep this to a technical discussion of my project, please?

:sigh:

Chill man! :D


:hijacked:

Can we please try and keep this to a technical discussion of my project, please?

:sigh:

Chill Dave!


Hey, if I really was the grumpy old fart that some people think I am, I would have locked the thread; <snip>

Whistle Cops or summat! :mrgreen:

Kin

Merlin
24th June 2009, 22:37
No worries, Charlie....... I'm just trying to stop this from going off at tangents.....

:thumbsup:

:grouphug:

Merlin
25th June 2009, 00:13
Arkanoid came through with the colour codes for the resistors and enough info to identify the values of the capacitors, so here's the final diagram as far as I can ascertain, with the values added:-

[attachment=0:cpoakhtr]Arkanoid.jpg[/attachment:cpoakhtr]

One thing I don't understand from this; pin 1 is an input and 2 an output, yet the input from pin 1 doesn't output on pin 2. Can anyone explain why all of the LEDs apparently work with this arrangement? It doesn't seem to make much sense.

Zetr0
25th June 2009, 05:17
@Merlicious

to be fair m8, that schematic is on crack, stick with the one you have developed me 'ol mucker and I believe it will work.

I have included some 7416N details

Merlin
25th June 2009, 15:04
@ Z

I know what you mean, mate; I kept going over and over the photographs and enhancing them for more detail, thinking I was screwing up, however, that diagram is 100% correct based on the photographs and arkanoid did his best on determining the colours of some really ancient resistors.

The only reason I did this was to preserve the design of the device Arkanoid discovered.